Wet etching of samarium selenium for piezoelectric processing

A subtractive forming method for piezoresistive material stacks comprising:

• masking a piezoresistive material stack to expose a first portion of the piezoresistive material stack and form a mask on a second portion of the piezoresistive material stack;
• applying an etch chemistry to the exposed first portion of the piezoresistive material stack, the etch chemistry including citric acid and hydrogen peroxide that is selective to an upper electrode layer of the piezoelectric material stack, wherein the hydrogen peroxide reacts with the upper electrode layer to provide an etch protectant surface on the upper electrode layer, and the citric acid etches a first element of a piezoelectric layer of the piezoelectric material stack selectively to the etch protectant surface leaving a residue of at least one second element of the piezoelectric layer on a dielectric layer of the piezoelectric material stack;
• and
• removing the residue of the at least one second element by elevating a temperature of the at least one second element above a heat of vaporization for the at least one second element, wherein the second portion of the piezoresistive material stack is protected from the removal and the heating by the mask.